The present invention relates to a boat engine for propelling a boat, and more particularly, to an outboard engine for propelling the boat.
Boat engines for propelling boats, which comprise a propulsion unit with an electric motor and a propeller powered by means of the electric motor, are known. Such boat engines are firstly known as on-board engines, which transfer the engine power of the electric motor to the propeller either via a fixed shaft system or a Z-drive in their conventional construction. Boat engines where the propulsion power is transferred to the propeller via a pod drive, for example, and also a pivotable pod drive, are also known.
As an alternative to this, so-called outboard engines are known, which are usually mounted on the stern of the boat to be propelled, and where a part of the outboard engine that lies above the waterline is connected with a part of the outboard engine that lies below the waterline via a shaft, on which the propeller is arranged.
Several construction types of outboard engines, which have a propulsion unit with an electric motor, are known, wherein there are, in particular, those outboard engines where the electric motor is arranged above the waterline, and the same is then connected to the propeller envisaged below the waterline via shafts and gears. In alternative embodiments, the electric motor is arranged in a housing lying below the waterline, and the electric motor acts on the propeller either directly or via a gear.
When electronically commutated electric motors are used and/or when electric motors where a speed regulation is realised electronically or by means of a series resistor are used, the corresponding power electronics for the electric motor can be above the waterline or below the waterline. A tightly spaced arrangement of the power electronics and the electric motor is often selected here. If the electric motor is, for example, located above the waterline, the power electronics can also be arranged above the waterline. If the electric motor is below the waterline, the power electronics can either be arranged above or also below the waterline.
Different construction types are also known for the power supply of outboard engines. It is, for example, known that the battery or the accumulator is fixed directly on the outboard engine, in a part of the outboard engine that lies above the waterline. Such outboard engines can be of a particularly compact construction, and form a self-contained unit, which is for example preferred for propelling smaller boats. The outboard engine will then require—in addition to the actual mechanical connection with the boat—no further installation or modification on the boat, and further installation space in the boat is not required.
In alternative embodiments, the battery or the accumulator is preferably located in the boat, and electricity is supplied to the part of the outboard engine located above the waterline via a corresponding supply cable.
All these boat engines, which comprise a propulsion unit with an electric motor, have in common that they usually have a rigid connection between the electric motor and the propeller. A neutral position, in which the combustion engine is uncoupled from the propeller by means of a gear, is, in particular, not normally envisaged—unlike with boat engines with a combustion engine. Combustion engines normally allow a possible starting of the engine only in a neutral position of the gear.
As a consequence, it is possible, with boat engines with a propulsion unit comprising an electric motor, that an accidental switch-on of the boat engine leads to an immediate rotation of the propeller, and therefore to a safety risk for persons nearby if the propeller is not in its actually envisaged condition, namely submersed in water.
This is the case in particular with outboard engines, and, most particularly, with portable outboard engines designed as a compact unit. An accidental switching on of the outboard engine can here also result in a “function control” of the outboard engine by the user, which is then operated by the user, or also during a service, in dry run outside of the water.
Even though operating instructions often include safety instructions in this regard and will point out that the boat engine must be mounted in its final position and operated only once the propeller is submersed, many users do not comply with these stipulations. A dry run operation of boat engines can lead to corresponding risks to persons nearby, to adjacent objects, as well as to the engine itself from the rotating propeller.
In addition it may result in an inadmissible heating up of the engine unit and/or the power electronics if the boat engine is not operated as instructed.
Based on this it is the object of the present invention to provide a boat engine that enables safer operation.
This object is solved by a boat engine for propelling a boat with the features described herein.
Accordingly a boat engine for propelling a boat, preferably an outboard engine for propelling a boat is suggested, comprising a propulsion unit with an electric motor and a propeller driven by means of the electric motor. According to the invention a water detection means is provided, which is adapted to detect whether the propeller is submersed in water.
The fact that the water detection means, which is adapted to detect whether the propeller is submersed in water or not, is provided means that it can be ascertained with the aid of the water detection means whether the boat engine is actually being operated in its intended regular position, namely in the position where the propeller is submersed, or not. If the boat engine is not operated in its intended position—and if the water detection means ascertains that the propeller is not submersed in water—corresponding measures can be carried out for preventing damage caused to the boat engine itself, the propeller, or nearby objects.
The power of the electric motor can for example be maintained at the power level at which the detection took place, or the power can be reduced or the electric motor can be stopped completely. In this way it can be ensured that a rotation of the propeller in a condition not submersed in water is possible only with limited or reduced power, or that such a rotation is completely prevented.
In this way risks to nearby persons, to surrounding objects and to the boat engine itself can be reduced or ruled out completely.
If power is for example kept constant or power is reduced in reaction to detecting that the propeller is not submersed in water, but the electric motor is not stopped completely, a function test can be carried out by the user prior to installing the boat engine or prior to pivoting the boat engine into its final stipulated position, in particular for boat engines designed as outboard engines, without the user having the feeling that the boat engine not yet installed could be defective.
The water detection means can contain a tilt sensor, with which the incline of the boat engine in relation to the horizontal and/or in relation to a component of the boat and/or the boat engine is determined. Such a tilt sensor can therefore, for example, determine the absolute position of the boat engine in space, for example by means of tilt sensors that measure the angle in relation to gravity or gravitation. Such a tilt sensor can however also be provided in the form of an angle sensor, which determines the angle of the boat engine in relation to a reference surface, for example in relation to a component of the boat engine such as for example a mounting plate or a mounting unit of the boat engine, or in relation to another component of the boat, for example the stern or the transom of the boat. If this results in the angle or the incline not complying with the predetermined angle or the predetermined incline that equals a correct mounting position, the water detection will signal that the propeller is not positioned in its regular submersed position.
The tilt sensor can also be designed as a positioning module or a satellite navigation system such as for example GPS, GLONASS, Galileo or Beidou installed in the boat engine, by means of which orientation is possible in addition to positioning.
The water detection means can also comprise a water sensor for detecting a submersion in water, wherein the water sensor is preferably provided in the vicinity of the propeller shaft of the boat engine. The water sensor can for example be arranged in a housing of the propulsion unit in the vicinity of the propeller shaft outlet. The water sensor can for example measure water wetting or water pressure. If the water sensor finds that it is not wet or that a stipulated hydrostatic pressure does not exist, the water sensor will correspondingly determine that the propeller is not correctly submersed in water.
In a further embodiment, the water detection means comprises a rev counter for determining the rotation speed of the electric motor and a power meter for determining the power of the electric motor (or torque meter for determining the torque of the electric motor), and the water detection means can be adapted for detecting whether the propeller is submersed in water during operation of the electric motor on the basis of the power characteristics (or the torque) of the electric motor in relation to the rotation speed of the electric motor. This makes use of the knowledge that the motor needs to compensate only no-load losses when the propeller is operated in air, and not in the submersed position. If the propeller is however submersed in water the absorbed and output power of the electric motor is substantially cubic as the rotation speed increases. An evaluation of the motor power compared to the rotation speed of the electric motor can consequently determine whether the propeller is submersed in water and whether a corresponding approximately cubic power curve related to a rotation speed curve occurs, or whether the absorbed or output power is quasi linear and only serves for compensating occurring no-load losses.
In this way it can be ascertained upon accidentally switching on the boat engine and when starting the propeller whether the propeller is submersed or not. This can preferably be realised by means of the components already provided in the boat engine in any case. Rotation speed measurement is normally provided for a boat engine with an electric motor, with which the rotation speed of the electric motor can then be set and also regulated or monitored, as the running modes for the boat engine stipulated by the respective user are normally converted into rotation speed stipulations. A rotation speed signal is normally also already provided and can be used for evaluating the water sensor.
A power meter can be used to measure power. Normally electric drives do however already include means, for example for measuring the torque, rotation speed, DC link current or the battery current and/or the DC link voltage or the battery voltage.
The power meter is preferably adapted accordingly to determine power on the basis of the rotation speed measured, the measured torque and/or on the basis of the DC link voltage and the DC link current and/or on the basis of the battery current and the battery voltage. Power can therefore be determined in the presence of the respective signals, for example as a product of torque and rotation speed, or as a product of DC link voltage and DC link current, or as a product of battery voltage and battery current. Torque can also be used on its own as a measure of power and can for example also be used on its own for determining operating points. As the corresponding measuring devices, and therefore the corresponding signals, are already provided, further construction measures can be omitted and the water sensor can revert to measurement signals that already exist, so that a cost-effective and very reliable solution for monitoring the submersion of the propeller in water during operation results here.
In an alternative or additional consideration only the torque is used. With a substantially constant and increasing propeller rotation speed, it can be assumed here that the propeller rotates in air, and only the bearing friction must be overcome. If the torque however increases quadratically as the propeller rotation speed rises, the propeller is submersed in water.
In this way a water detection that is independent from the pitching or rolling of the boat and from different installation positions or installation angles of the respective boat engine, as is essentially the case with an incline determination, can correspondingly also be carried out.
In one preferred further development a control unit for controlling the power of the electric motor is provided, wherein the control unit communicates with the water detection, and the control unit can maintain and/or limit and/or reduce the power and/or rotation speed and/or torque of the electric motor or stop the electric motor upon detection of a propeller that is not submersed in water. In this way a direct and safe limiting of the power and/or the rotation speed and/or the torque of the boat engine or a stopping of the boat engine results to prevent damage, accidents and injuries caused by an incorrectly arranged or installed boat engine.
In at least one embodiment, the control unit is adapted for allowing a renewed increase in power and/or the rotation speed and/or the torque or a renewed starting of the electric motor only after the limiting and/or maintaining and/or reducing of power and/or the rotation speed and/or the torque and/or after stopping the electric motor, if a running mode adjuster for stipulating a running mode has been set to a lower running mode or to a zero position. In this way it can be prevented that a sudden start or a sudden increase in power, the rotation speed or the torque occurs when the propeller is submersed in water and an uncontrolled action of the boat engine results from the same.
This is of particular importance also when the power and/or the rotation speed and/or the torque of the electric motor is reduced or switched off when a boat capsizes and until it has righted itself again. In such a case, and especially if persons have gone overboard, an automatic renewed switching on of the electric motor or an increase in power, rotation speed and torque can be dangerous for persons still in the water or can make it impossible for such persons still in the water to reach the boat upon renewed contact of the propeller with water. In an extreme case the boat would carry on travelling driverless and would leave persons still in the water behind.
In one further development a short-term reduction in the power of the electric motor during a brief emersion of the propeller can be realised, for example, if the boat is lifted by waves in such a way that the propeller is briefly surrounded by air or, because a boat that is hydro-foiling jumps across the waves. In this way an uncontrolled speeding up of the propeller upon emersion from the water can be avoided and the entire battery power used can be reduced in this way and wear will be less.
In order to not bring about an undesired reduction in power, torque or rotation speed, or even a switching off of the boat engine during normal operation of said boat engine when the propeller is briefly lifted out of the water due to boat movements the water detection, and preferably also the interference with the torque, the rotation speed or the power of the electric motor connected with the same during normal operation can be switched off. Such switching off can for example be triggered in that the water detection detects that the propeller is submersed when the electric motor is first switched on or started up—for example also within a predetermined period of time. If this is the case, the water detection will then be switched off.
A reaction time can also be defined in order to avoid disadvantageous effects, upon expiry of which a maintaining or reducing of power, of torque or of the rotation speed or a switching off of the electric motor is carried out.
Reducing the rotation speed or the power or the torque, or switching off the electric motor can also be realised by means of a predetermined control curve, for example a flat ramp, as shown, for example, in FIG. 3, so that no abrupt reduction in rotation speed and/or power and/or torque will occur.
Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the presently described embodiments.